1. Field of the Invention
This invention relates to the conversion of butenes especially isobutene by dimerization to highly branched octenes especially trimethylpentenes and dimethylhexenes, in the presence of a catalyst. This invention also pertains to the use of specific zeolite and/or zeo-type containing catalyst.
Trimethylpentenes are highly valuable intermediates for the production of isooctane by hydrogenation. In addition, both the trimethylpentenes and dimethylhexenes may be used as intermediate for the production of xylenes especially p-xylene. Isooctane and p-xylene are valuable chemicals for gasoline blending and the manufacture of polyester fiber respectively.
2. Description of the Prior Art
Dimerization of butenes especially isobutene is a commercially important reaction. Many catalysts have been claimed for this reaction. For example supported and promoted sulfuric acid and phosphoric acid, and a variety of other catalysts have been claimed in U.S. Pat. Nos. 3,760,026. 5,118,900 describes the dimerization of isobutene over zeolite Y or a modified zeolite Y. However, these catalysts also produce oligomers of isobutenes. European Patent 0 247 802 describes the isomerization of olefins especially butenes to produce isobutenes over uni-directional medium pore zeolites whereas European Patent 0 124 998 describes the production of transport fuel from small olefins by oligomerization, cracking, and isomerization over medium pore zeolites.